The present invention is directed to a hypodermic injection device (e.g., a hypodermic syringe). More particularly, the present invention is directed to such a hypodermic injection device wherein, after use of the needle for injection, the needle can be withdrawn into the hypodermic reservoir chamber (that is, the chamber that held the injectable material) so that the needle is no longer exposed after use.
An increasing problem for health care professionals is on-the-job contamination by used hypodermic needles. Because of the hundreds of needles used in hospital and office settings each week, it has been estimated that a puncture wound from used needles occurs as often as once every one or two weeks per health care worker. With the outbreak of AIDS and other deadly blood-borne diseases, this has become an area of increasing concern. Likewise, the sharing of needles by drug abusers, and even sharing in the clinical environment, represents a real threat to the public.
Various prior devices have been developed in order to withdraw the hypodermic needle into the hypodermic reservoir chamber after use, to completely isolate the needle immediately after the patient is injected and to allow the hypodermic reservoir chamber to be subsequently discarded with the needle therein. One prior device is shown in U.S. Pat. No. 4,813,936. This patent describes a needle assembly for the hypodermic syringe including a hollow needle with an inner end inside the hypodermic reservoir chamber which held the injectable material, the reservoir chamber including a passage through which the needle extends and is slidable, the needle having stop means limiting outward movement of the needle relative to the reservoir chamber but not limiting inward movement of the needle as the needle is withdrawn into the reservoir chamber. This patent discloses that the plunger used to cause emptying of the injectable material that was held within the hypodermic reservoir chamber, slidably mounted within such chamber, has an end closest to the needle that is made of a plug of relatively soft material, while the end of the needle within the chamber includes structure (such as barbs) which can enter the soft material. Upon use, the plunger is depressed such that the end of the needle within the chamber pierces the end of the plug and is retained therein due to the plurality of barbs. Once engagement of the needle and plug has occurred, the plunger can then be withdrawn whereby the needle engaged to the plug is also withdrawn into the reservoir chamber.
However, the design shown in U.S. Pat. No. 4,813,936 requires a relatively complex needle structure, undesirably increasing the cost of the needle and, accordingly, the overall cost of the hypodermic syringe.
U.S. Pat. No. 4,826,484, the contents of which are incorporated herein by reference, also discloses a syringe having a retractable needle, the syringe including a cylinder or barrel having a closed distal end and an open proximal end, with a first end of the needle projecting outwardly from the distal end of the cylinder, and by which a fluid may be injected; a second end of the needle extends into the interior of the cylinder, and terminates at a relatively large needle catch. The syringe includes a plunger which is adapted for reciprocal and axial movement through the syringe cylinder, the plunger including a detachable connection of an elongated stem to a sealing and locking assembly. An elastomeric seal is formed at one end of the sealing and locking assembly, and functions as a plunger head when the plunger is moved axially through the cylinder during a fluid injection procedure. The seal is mounted around a plurality of flexible legs which define a needle capturing receptacle therebetween. When the plunger is moved through the syringe cylinder at the conclusion of a fluid injection procedure, the seal is pressed against the most distal aspect of the cylinder, such that the needle capturing receptacle is advanced axially into engagement with the needle catch; the needle catch is thereby received by the needle capturing receptacle, and upon withdrawal of the plunger back into the cylinder the needle is also withdrawn into the cylinder.
The needle structure disclosed in U.S. Pat. No. 4,826,484 requires a needle catch at the end of the needle, such needle catch being an enlarged structure formed at the end of the needle within the syringe cylinder, and also requires a relatively complex locking assembly for the plunger, including a plurality of flexible legs for retaining the needle in the plunger. Such relatively complex structure for both the needle and plunger increases the complexity of manufacturing the syringe, and increases the cost thereof.
U.S. Pat. No. 4,838,870 also discloses a syringe having a retractable needle, with the end of the needle having an enlarged portion at the end which can be captured by a needle capturing receptacle in the end of the plunger, similar to the structure described in the previously discussed U.S. Pat. No. 4,826,484. U.S. Pat. No. 4,838,870 further discloses that the needle also includes a further thickened portion, which is larger than the diameter of the hole in the syringe cylinder through which the needle extends out of the cylinder, for preventing movement of the needle in a direction out of the cylinder. U.S. Pat. No. 4,838,870 also discloses that the needle and support therefor can be independent of the syringe cylinder and removably attached thereto, so that different needles (for example, having different needle sizes) can be used with the same syringe cylinder.
U.S. Pat. No. 4,804,370 discloses a syringe having a retractable needle, wherein the needle has a thickened portion at the end thereof adapted to be retained in a needle capturing receptacle at the end of the plunger, similar to the structure previously described in connection with U.S. Pat. No. 4,826,484. U.S. Pat. No. 4,804,370 further discloses that the flexible legs of the needle capturing receptacle should have an offset configuration so that when the used needle is withdrawn into the syringe cylinder, the used needle will be canted or slanted relative to the vertical, whereby the needle is misaligned with respect to the opening in the end of the cylinder. Due to such misalignment, the needle cannot be repositioned so as to extend outside the cylinder for re-use. Moreover, after withdrawal of the needle into the cylinder, the plunger can again be moved in the chamber so that the slanted (misaligned) needle will contact a wall of the cylinder and be bent or destroyed within the cylinder.
While U.S. Pat. No. 4,804,370 discloses specific structure both for capturing the needle for withdrawal thereof into the chamber and for destroying the needle in the chamber, the described structure (including the offset configuration of the flexible legs forming the needle capturing receptacle) is complex, and increases manufacturing costs.
Accordingly, it is still desired to provide a hypodermic injection device wherein the needle can be withdrawn into the reservoir chamber after use, which device and needle structure is relatively simple and can be manufactured inexpensively. It is particularly desired to provide a hypodermic injection device wherein the needle structure for the device can be simply and inexpensively manufactured, without sacrificing effectiveness of the structure for reliably capturing and retracting the needle into the hypodermic reservoir chamber. Moreover, it is also desired to provide such a hypodermic injection device, wherein the needle can be withdrawn into the reservoir chamber and prevented from being moved out of the reservoir chamber into a position for re-use, with simple structure that is easily and inexpensively manufactured. It is also desired to provide a hypodermic injection device having a retractable needle, wherein, prior to use, accidental retraction of the needle into the reservoir chamber can be avoided.